1. Field of the Invention
The present invention relates to a keyboard apparatus provided with pivotal members that each perform pivotal motion in accordance with a key depressing operation.
2. Description of the Related Art
In a keyboard apparatus with a keyboard of a translation type in which each key is vertically translated, it is easy to make uniform the key depression stroke and touch weight of each white key and those of each black key. However, in a keyboard apparatus configured such that each key is pivotally moved about its key pivot in the vertical direction, the distance between a portion of the key operated for key depression and the key pivot is shorter in black keys than in white keys, so that it is difficult to secure a sufficient key depression stroke for each black key without special design, and the tough weight of each black key tends to increase.
To overcome this problem, a keyboard apparatus has been proposed in which the key pivot of the black key is located rearward of that of the white key so as to keep the touch feeling of the white key and that of the black key in a somewhat more balanced state (see Japanese Laid-Open Patent Publication (Kokai) No. S60-52439).
On the other hand, keyboard apparatuses are also known in which mass bodies are mounted on a key frame or the like in a manner pivotally movable about respective pivotal motion supports, each for applying an appropriate inertial force to the associated key when the key is depressed. In a keyboard apparatus of this type, in general, when a key is depressed, a driven part of the associated mass body is driven by a driving part of the key, whereby the mass body is pivoted in accordance with the key depression.
Further, this type of keyboard apparatus provided with the mass bodies is configured, for example, such that the pivotal motion supports for all the mass bodies associated with the respective black and white keys are arranged at the same longitudinal (front-rear) location, whereas the driven part of the mass body for each black key is located forward of that of the mass body for each white key. That is, the principle of leverage is utilized to secure an appropriate key depression stroke of the black key and at the same time minimize the difference between the touch feeling of the white key and that of the black key.
However, since the driven part of the mass body for each black key is located forward of that of the mass body for each white key as described above, the length of the mass body for the black key becomes longer, and hence the space of a portion in the longitudinal direction of the keyboard apparatus where the mass bodies are to be arranged is reduced.
For keyboard apparatuses, there have been proposed various configurations of the pivotal motion support for pivotally supporting a pivotal member (a key, a mass body, or the like) which performs pivotal motion in accordance with key depression. Particularly, one of the configurations is characterized in that the pivotal motion supports are provided on ribs extending in the vertical and longitudinal directions. Further, some pivotal motion-supports are configured such that the ribs are integrally formed with a resin-made key frame by injection molding using a mold.
In this case, ribs provided for keys adjacent to each other are very close to each other, and further each rib is in the form of a flat plate. This brings about the problem that the thickness of projections and the like of the mold, for forming the respective ribs, is inevitably required to be reduced, which reduces the strength of the mold.